参考 [https://www.zhihu.com/question/453677175](https://link.segmentfault.com/?enc=%2Feok54EXUYDf2ZmMmDge6A%3D%3D.t%2FDkDJrpw%2Bg7JTzBcKKXEMergJwuOlUZcMESxQNQ3tPEOh93Enc6fpfJGCdQ%2BvhL) 记住`return Promise.resolve()`、 `return new Promise(resolve => { reolve() })` 与 `return new Promise(resolve => { reolve() }).then(res => {return res})`这三个返回值会卡两次